1. Field of the Invention
The present invention relates to a hard disk drive. More particularly, the present invention relates to a hard disk drive having a filter for filtering particles within a casing of the hard disk drive.
2. Description of the Related Art
Hard disk drives (HDDs) are memory devices which can record and reproduce large amounts of data at high speed. Accordingly, HDDs are widely used as auxiliary memory devices for computer systems. Recently, there has been a demand for a compact HDD which can be used in portable electronic devices such as laptop computers, PDAs, and mobile phones. In fact, a compact HDD having a diameter of 0.85 inches, similar to that of a coin, has been actually developed and is expected to be used for mobile phones in the near future.
Typically, an HDD includes: a disk on which data is recorded, a spindle motor for rotating the disk, an actuator arm having a magnetic head that can record data on the disk and/or reproduce data from the disk, a support shaft that supports the actuator arm with the magnetic head disposed above a recording surface of the disk, and a voice coil motor (VCM) for swinging the actuator arm about the longitudinal axis of the support shaft to position the magnetic head over the disk. More specifically, the actuator arm is swung around the axis of the support shaft when power is applied to the spindle motor to rotate the disk and to the voice coil motor (VCM) to supply current to the voice coil motor (VCM). At this time, the magnetic head is moved over a recording surface of the rotating disk to read or write data from or onto the disk. Also, the HDD includes a base to which the aforementioned components are mounted, and a cover that is assembled to the base to enclose the components.
However, such an HDD is extremely vulnerable to particles such as dust or foreign materials. For example, particles can adhere to the recording surface of the disk. In this case, errors are very likely to occur during the recording and/or reproducing of data. Also, the magnetic head may be damaged. Accordingly, the base and cover of the HDD are generally assembled to each other after particles have been completely removed from the components that are to be enclosed by the cover. Regardless, particles can still intrude into the HDD during assembly or through air that enters the assembled HDD and remain on the disk. Each of the particles typically has a diameter of less than about 0.3 μm.
Thus, an air filter is provided on the cover to remove particles in the HDD. The air filter is disposed in a corner of the inner surface of the cover. The air filter is narrow and is oriented perpendicular to the recording surface of the disk. Therefore, the air filter filters particles thrown off of the outer peripheral portion of the disk due to the rotation of the disk.
However, the linear velocity of the outer peripheral portion of the rotating disk is greater than that of the inner peripheral portion thereof. Therefore, particles on the outer peripheral region of the disk are flung off of the disk at a relatively high velocity and are then trapped as they pass through the filter. In contrast, particles on the inner peripheral portion of the disk having a relatively low velocity. In particular, the linear velocity of the inner peripheral portion of a disk of a micro drive is low because the disk is small and the rate (RPMs) at which the disk is rotated is low. Thus, the particles on the inner peripheral portion of the disk tend not to move very far from the inner peripheral portion when the disk is rotating. Hence, these particles are never filtered out and the particles remain on the disk. Therefore, the magnetic head may be damaged by the particles or errors may occur during the recording and reproducing of data. Also, in a conventional HDD in which the disk has recording surfaces on both sides thereof, particles on the lower recoding surface of the disk are not removed by the filter.